1. Field of the Invention
This invention is directed toward a method of calculating the total laser energy needed to produce one or more selected laser induced surface modification reactions in a substrate moving relative to a laser beam. The present invention is further directed to a method for programming a programmable feedback control system with the calculated total laser energy such that the control system may be used to control laser beam power level and beam width in a process for producing a laser induced surface modification.
The present invention relates to the field of treating metallic surfaces subject to wear, oxidation, corrosion and rusting.
2. Description of the Prior Art
In the past, substrate materials have been irradiated at preselected power levels in order to produce a laser induced surface modification. It is desirable to control the depth and chemistry of laser modifications produced by such processes. Prior art methods of practicing laser induced surface modifications have failed to incorporate a dynamic feedback control system for controlling variables such as laser power, laser beam width, or the rate of movement of the substrate being irradiated relative to the laser beam in order to control the laser induced surface modification.
Prior art methods of practicing laser induced surface modification have failed to calculate the total laser energy needed for one or more specific preselected reactions and then to program a feedback control system to operate a laser at that selected power level. The present invention provides such a method of programming a feedback control system in order to practice a laser induced surface modification.
Exposed metallic surfaces, such as steel and aluminum, are subject to corrosion, rust, hydrogen embrittlement and wear flash erosion. Typically, these surfaces are protected by painting, cladding, coating or electroplating the surface. These methods, however, require frequent reapplication and are subject to flaking and separation of the protective layer from the substrate surface at the junction of the protective layer and the substrate.
The present invention is directed toward a method of calculating the total laser energy needed to produce one or more selected laser induced surface modification reactions in a substrate moving relative to a laser beam. The term xe2x80x9creaction(s)xe2x80x9d is used herein to refer to one or more reactions. The invention comprises selecting a reaction(s) to be induced, selecting the temperature, T, at which each selected reaction shall take place, and determining the free energy of formation, FEF, of each selected reaction at the selected temperature for each reaction.
The invention further comprises selecting the depth of the surface modification, D, selecting the volume fraction, VF, of the surface modified layer, and selecting the translation rate, TR, of the relative movement of the substrate with respect to the laser beam. The phrase xe2x80x9crelative movementxe2x80x9d, as used herein, encompasses movement of the substrate relative to a stationary laser beam, movement of a laser beam relative to a stationary substrate, and movement of both the laser beam and the substrate.
The invention further comprises determining the coating species theoretical density, CSD, based upon the selected reaction(s), selecting the laser beam width, BW, and calculating the mass of alloying coating species, MAS, needed.
The method of the present invention further comprises calculating the total laser energy, TLE, needed to produce the surface modification having the volume composition, VF.
The present invention provides metallic surfaces subject to wear, oxidation, corrosion and rusting with a surface alloy layer for protecting such metallic surfaces without the flaking and separation, and the need for frequent reapplication, of prior surface treatments.
This and other objects are achieved in accordance with the present invention with a process by which a metal substrate surface is treated or otherwise protected from wear, corrosion by the formation of an alloy in the surface and subsurface of the substrate. The alloy forms an integral part of the substrate, in contrast to other methods of protecting metal surfaces, such as coating, cladding, painting and electroplating.
According to the process of the present invention, which will be referred to as xe2x80x9claser induced surface improvementxe2x80x9d (or the LISI process), a desired alloying metal is applied to a metal surface to be treated, and is irradiated by means of a laser beam. The process results in the formation of an alloy in the surface of the metal. The major components of a system for performing the process of the present invention are a laser, a corresponding delivery system, a movement system, a control system (including quality control), and a precursor alloying material, such as a powder in a binder.